1. Field of the Invention
The present invention relates to a communication system and its method for transmitting data in a spread spectrum system using frequency hopping.
2. Description of the Related Art
For example, Asynchronous Decentralized DS-CDMA Using Feedback-Control Spreading Sequences for Time-Dispersive Channels, (Kazuki CHIBA, Masanori HAMAMURA and Shin'ichi TACHIKAWA, IEICE TRANS COMMUN, VOL. E91-B, NO1. JANUARY 2008, PAPER, Special Section on Cognitive Radio and Spectrum Sharing Technology, The Institute of Electronics, Information and Communication Engineers) discloses a communication system configured such that any two communication devices are taken from a large number of communication devices to make a plurality of pairs of communication devices, each pair capable of transmitting data in an asynchronous DS-CDMA (Direct-Sequence Code Division Multiple Access) system.
Iterative Construction of Optimum Signature Sequence Sets in Synchronous CDMA systems, (S. Ulukus et. al., IEEE Trans. Inform., Theory, vol. 47, no. 5, pp. 1989-1998, July 2001) discloses a communication system where a receiving device feeds back a hopping pattern to a transmitting device.
Address Assignment for a Time-Frequency-Coded Spread-Spectrum System (G. Einarson, Bell Syst. Tech. J., vol. 59, no. 7, pp. 1241-1255, September 1980) discloses an initial value of a hopping pattern P.
Multitone-Hopping CDMA Using Feedback-Controlled Hopping Pattern for Decentralized Multiple Access (IEICE Trans. Fundamentals, vol. E91, No. 12, December 2008) discloses a method in which a transmitting device adjusts parameters for generating transmission signals based on information fed back to the transmitting device from a receiving device for the purpose of improving reception quality of transmission signals at the receiving device.